Revision e6da7c9fed111ba1243297ee6eda8e24ae11c384 authored by Eric Sandeen on 23 May 2009, 19:30:12 UTC, committed by Felix Blyakher on 02 June 2009, 03:59:38 UTC
In the case where growing a filesystem would leave the last AG too small, the fixup code has an overflow in the calculation of the new size with one fewer ag, because "nagcount" is a 32 bit number. If the new filesystem has > 2^32 blocks in it this causes a problem resulting in an EINVAL return from growfs: # xfs_io -f -c "truncate 19998630180864" fsfile # mkfs.xfs -f -bsize=4096 -dagsize=76288719b,size=3905982455b fsfile # mount -o loop fsfile /mnt # xfs_growfs /mnt meta-data=/dev/loop0 isize=256 agcount=52, agsize=76288719 blks = sectsz=512 attr=2 data = bsize=4096 blocks=3905982455, imaxpct=5 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 log =internal bsize=4096 blocks=32768, version=2 = sectsz=512 sunit=0 blks, lazy-count=0 realtime =none extsz=4096 blocks=0, rtextents=0 xfs_growfs: XFS_IOC_FSGROWFSDATA xfsctl failed: Invalid argument Reported-by: richard.ems@cape-horn-eng.com Signed-off-by: Eric Sandeen <sandeen@sandeen.net> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Felix Blyakher <felixb@sgi.com> Signed-off-by: Felix Blyakher <felixb@sgi.com>
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io_ordering.txt
On some platforms, so-called memory-mapped I/O is weakly ordered. On such
platforms, driver writers are responsible for ensuring that I/O writes to
memory-mapped addresses on their device arrive in the order intended. This is
typically done by reading a 'safe' device or bridge register, causing the I/O
chipset to flush pending writes to the device before any reads are posted. A
driver would usually use this technique immediately prior to the exit of a
critical section of code protected by spinlocks. This would ensure that
subsequent writes to I/O space arrived only after all prior writes (much like a
memory barrier op, mb(), only with respect to I/O).
A more concrete example from a hypothetical device driver:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
...
In the case above, the device may receive newval2 before it receives newval,
which could cause problems. Fixing it is easy enough though:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: (void)readl(safe_register); /* maybe a config register? */
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: (void)readl(safe_register); /* maybe a config register? */
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
Here, the reads from safe_register will cause the I/O chipset to flush any
pending writes before actually posting the read to the chipset, preventing
possible data corruption.
Computing file changes ...